Iowa resident here...Your goal of 140+ to 150 is reasonable even if your odds are somewhere under 50% for a week hunt in the rut. Your goal of 5+years old is very low odds anywhere in the state. Not impossible but low odds. There are a lot more 140+ inch 3 year olds running around than 5+...
Another Goodyear Duratrack fan here. It took me a lot of years to convince myself to spend that much money but I love them in mud and snow in the Midwest.